Despite what you all think, I think "Wii" is a pretty innovative name.
I think it looks independent and different from the names "Xbox 360" and "Playstation 3", showing that it attracts a different crowd and therefore a different part of the market. The system is also just as different as the name, making "Wii" a very appropriate way to name the console, since the sole fact that they are different from the rest of the market fits them together so well. It's very memorable that way.